Ionizing device for electrical precipitators



Feb. 20, 1951 H. KLEMPERER 2,542,035

IONIZING DEVICE FOR ELECTRICAL PRECIPITATORS Filed June 20, 1946 1296. IA C B A C B A C B A C B ICBACB.A

//v vEN TOR HANS KL EMPER ER Patented Feb. 20, 1951 IONIZING DEVICE FORELECTRICAL PRECIPITATORS Hans 'Klemperer, Belmont, Mass., assignor toRaytheon Manufacturing Company, Newton, Mass., a corporation of DelawareApplication June 20, 1946, Serial No. 678,155

Claims. 1

This invention relates to electrical precipitators, for electricallyseparating smoke and dust from air, flue gases and the like. Asheretofore constructed it has been necessary to supply high voltagedirect current to the ionizing wires of the precipitators. This requiresrectifying tubes capable of handling such high voltages in order tosupply the direct current from the usual alternating current supplysource. Where it is attempted to use alternating current directly forionizing purposes, only the positive peaks of the 60 cycle waves ionizethe air and the time. be tween peaks is lost for ionizing action.

.It is among the objects of the present invention tov provide vaprecipitator in which the ionizing device maybe. supplied withalternating current without the necessity of providing rectifiers.

The above and other objects and features of the invention will be madefully apparent to those skilled in the art from a consideration of thefollowing detailed description taken in conjunction with theaccompanying drawing in which:

i .Fig. 1 is a diagrammatic view of an electrical precipitatorconstructed in accordance with the invention;

Fig. 2 is a diagram useful in explaining the 0pvelation of theinvention; and

Fig. 3 is a time-voltage graph illustrating the operation of theinvention.

Referring to the drawing, reference numeral l0 indicates generally athree-phase transformer having A-connected primary windings E l and Y-connected secondary windings L2. The outer terminals it, i l and 15 ofthe Y secondary windings of the transformer Ill are directly connected,respectively, to the ionizing Wires A, B and C of an ionizing .deviceit. The neutral point ll of the secondary windings is connected directlto the outer metallic casing iii of the ionizing chamber l6.Preferably'the connection between the centerpoint Hand the casing is isgrounded. The wire electrodes A, B and C of the ionizing device arearranged in parallel relation and so spaced with respect to thedirection of air how and the speed of the air passing through thechamber 18 that during operation the air passing through the chamber issubjected, at all times, to the ionizingaotion .of at least one of theelectrodes A, B and C. The proper spacing of the electrodes in .orderthat each of them will be effective in ionizing the air is given 'by theformula where a isthe distance between two successive electrodes; 12 isthe speed of air; n the number of phases of the power supply; and f thefrequency in cycles per second.

When the wires are so spaced it will be seen that if the positive peakof one phase is effective at A, the body of air flowing from A to B willbe ionized during this positive peak. The air between B and C will beun-ionized, the condition of the air at the end of this first positivepeak effective at A being shown in column I of Fig. 2 in which thestipplin'g represents ionized air. If the positive peak of the nextsuccessive phase is effective at C, the air flowing between B and C willnow be ionized as it passes C. The body of ionized air between A and Bwill at the same time move to the space between B and C while a body ofun-ionized air flows into the space between A and B, the condition ofthe air at the end of the'second positive peak being shown in column IIof Fig. 2. If the positive peak of the third phase is now effective atB, then the unionized air between A and B will be ionized during thisperiod as it moves past B. The condition of the ionized air at the endof the third phase is shown in column 111 of Fig. 2. The cycle may thenbe repeated, the first phase of the second cycle being effective at A toionize a body of incoming air as it passes into the space between A andB. At the end of the first phase of the second cycle the condition ofthe air will be as indicated in column IV of Fig. 2, in which it will beseen that the column of air ionized during the preceding cycle has movedpast C. A body of un-ionized air is present between B and C while thebody of air between A and B has been ionized. On the next succeedingphase the positive peak will again be effective at C to ionize the bodyof ionized air between B to C as it moves pastC, andthe ionized airspaced between A and .B will during this period move in the spacebetween B and C. The condition of the air at the end of this secondphase of the second cycle will "VI of Fig. 2. The cycle thus repeatsitself, and

it will be seen that if the positive peaks of the thirdphase areefiective in the order A, C, B, then each of the ionizing wires will beeffective dur- .odes of tubes 22, 23 and 24. .and 24 are preferably ofthe gas-filled type having the periods when un-ionized air is passingenergized electrode and all portions of the air passing through thedevice are acted upon by at least one of the ionizing electrodes.

Referring to Fig. 3, the three phases from the transformer secondarywindings I2 are illustrated graphically, about an axis DD. The positivepeaks of the first phase are denominated l P and the negative peaks IN.The positive and negative peaks of the second and third phases arecorrespondingly 2P, 2N, 3P and 3N, respectively. The positive voltagevalues above line E-E are above the level at which ionization ofparticles lying between any one of the electrodes A, B or C and casing[8 takes place. The areas of the curves above this line are shaded. Thenegative voltage values below line F-F are also above the level (in thenegative direction) at which ionization of particles lying between theelectrodes A, B or C and easing I8 takes place. It has long beenrecognized thatwith asymmetric electrodes such as A and casing l8ionization occurs more readily when the smaller electrode is positivewith respect to the larger electrode than when the polarity is reversed.This gives rise to a rectifying action due to the electrodes themselves.See for example Lissman Patent No. 2,326,237. Thus, with a givenpeak-to-peak voltage, the negative peaks may be made substantiallycompletely ineifective, so that line F-F in Fig. 3 is moved below thenegative peaks. As is apparent from the foregoing description, when thephase between electrode A and casing I8 is regarded as the first phase,the second phase is between electrode C and the casing, and the thirdphase is between electrode B and the casing, as is indi cated in Fig. 3.Considering, therefore, only the positive peaks, it is apparent that theair passing between A and casing l8, that is, from A to B, is ionizedduring the shaded portion of the peak. Thereafter, the air flowingbetween C and casing [8, that is, from C out of the casing, is ionizedduring the shaded portion of the positive peak of the second phase.Thereafter, the air which is flowing between B and casing 18, that is,from B to C, is ionized during the shaded portion of the positive peakof the third phase.

The ionized air on passing from the ionizing chamber It may beprecipitated on the plates of a precipitator chamber which may be ofconventional design. In the instance shown, in order to supply aprecipitating volta e to the precipitator plates at a lower voltage thanthat supplied to the ionizing device. center taps I9, 20 and 2| areprovided on each of the windings of the secondary E2 and connected,respectively, to the oath- The tubes 22, 23

wire electrodes A, B and C may be of the order of 12,000 volts and thisvoltage is applied without the intervention of rectifiers between .the

source of supply and the ionizing wires. The

4 potential on the charged plates l3 may be of the order of 6000 volts.

While there has been herein described a preferred embodiment of theinvention, other embodiments within the scope of the appended claimswill be obvious to those skilled in the art from a consideration of theform shown and the teachings hereof.

What is claimed is:

1. An ionizing device for an electrical precipitator comprising aplurality of spaced ionizing electrodes, a source of raw polyphasealternating potential for energizing said electrodes, the number ofphases of said source being equal to the number of said electrodes and aseparate one of said electrodes being connected directly to each of thephases of said source, whereby the peaks of said alternating potentialare applied to first one and then another of said electrodes in apredetermined sequence and whereby all of said electrodes are suppliedwith alternating potential'of the same frequency, means for passing thegas to be cleaned past each of said electrodes in suc-' cession, saidelectrodesbeing so spaced with re lation to the velocity of said gasthat each of said electrodes acts on an un-ionized portion of said gasand all portions of said gas are acted upon by at least one of saidelectrodes. 1

2. An ionizing device for an electrical precip itator comprising aplurality of spaced ionizing electrodes, a source of raw polyphasealternating potential for energizing said electrodes, the num; ber ofphases of said source being equal to the number of said electrodes and aseparate one of said electrodes being connected directly to each of thephases of said source, whereby the peaks of said alternating potentialare applied to first one and then another of said electrodes in apredetermined sequence and whereby all of said elec trodes are suppliedwith alternating potential of the same frequency, a grounded electrodecoacting with all of said ionizing electrodes to provide ionizingdischarges therebetween, said grounded electrode defining a channel forpassing the gas to be cleaned past each of said ionizing electrodes insuccession, said ionizing electrodes being so spaced with relation tothe velocity of said gas that each of said ionizing electrodes acts onan un-ionized portion of said gas and all portions of said gas are actedupon by at least one of said ionizing electrodes.

3. An ionizing device for an electrical precipi tator comprising aplurality of fine wire ioniz ing electrodes extending in spaced parallelrela-' tion in a common plane, a source of raw poly+ phase alternatingpotential for energizing said electrodes, the number of phases of saidsource being equal to the number of said electrodes and a separate oneof said electrodes being connected directly to each of the phases ofsaid source, whereby the peaks of said alternating potential are appliedto first one and then another of said electrodes in a predeterminedsequence and whereby all of said electrodes are supplied withalternating potential of the same frequency, a grounded electrodecoacting with all of said ionizing electrodes to provide ionizingdischarges therebetween, said grounded electrode defining a channel forpassing the gas to be cleaned past each of said ionizing electrodes insuccession in a direction parallel to the common plane thereof; saidionizing electrodes being so spaced with relation to the velocity ofsaid gas that each of said ionizing electrodes acts on an un-ionizedportion of said gas and all portions of said gasareelectrodes, a sourceof raw polyphase alternatingpotential of a predeterminedfrequency forenergizing said electrodes, the number of phases of said source beingequal to the number of said electrodes and a separate onev of saidelectrodes being connected directly to each of the phases of saidsource, whereby the peaks of said alternating potential are applied tofirst one and then another of said electrodes in a predeterminedsequence, means for passing the gas to be cleaned past each of saidelectrodes in succession at a predetermined velocity, the spacingbetween said electrodes being equal to f where v is the velocity of saidgas, n is the number of phases of said source, and f is the frequency ofsaid source.

5. An ionizing device for an electrical precipitator comprising aplurality of spaced ionizing electrodes, a source of raw polyphasealternating potential of a predetermined frequency for energizing saidelectrodes, the number of phases of said source being equal to thenumber of said electrodes and a separate one of said electrodes beingconnected directly to each of the phases of said source, whereby thepeaks of said alternating potential are applied to first one and thenanother of said electrodes in a predetermined sequence, a groundedelectrode coacting with-all of said ionizing electrodes to provideionizing discharges therebetween, said grounded electrode defining achannel for passing the gas to be cleaned past each of said ionizingelectrodes in succession at a predetermined velocity, the

spacing between said electrodes being equal to f where o is the velocityof said gas, n is the number of phases of said source, and f is thefrequency of said source.

HANS KLEMPERER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

